Pivotal arm band saw

ABSTRACT

A band saw having a pivotal arm supported for articulation on both sides of the saw blade and preferably above the surface upon which the work is to be cut is disclosed. The band saw includes a frusto-conical drive wheel and means for guiding the saw blade in slip condition on said drive wheel. Also disclosed are guide means carried by the pivoted arm and formed to direct coolant on the saw blade as well as impart a positive camber to the blade. The saw is provided with a fluid activated controlling means for raising and lowering the pivotal arm which includes a combined gas-liquid system in which the flow rates of the gas and liquid may be pre-selected to control the rate of descent of the arm.

Elite Harris States Patent [1 1'- Nov. 19, W74

[ PIVOTAL ARM BAND SAW [76] Inventor: Gerald R. Harris, Livermore,Calif.

[22] Filed: Aug. 8, 1972 [21] Appl. No.: 278,851

Related US. Application Data [62] Division of Ser. No. 86,732, Nov. 4,1970, Pat. No.

Primary ExaminerDonald R. Schran Attorney, Agent, or Firm Warren, Rubin& Chickering 57 ABSTRACT A band saw having a pivotal arm supported forarticulation on both sides of the saw blade and preferably above thesurface upon which the work is to be cut is disclosed. The band sawincludes a frusto-conical drive wheel and means for guiding the sawblade in slip condition on said drive wheel. Also disclosed are guidemeans carried by the pivoted arm and formed to direct coolant on the sawblade as well as impart a positive camber to the blade. The saw isprovided with a fluid activated controlling means for raising and lowering the pivotal arm which includes a combined gasliquid system inwhich the flow rates of the gas and liquid may be pre-selected tocontrol the rate of descent of the arm.

2 Claims, 13 Drawing Figures PATENIE' :mv 1 91974 SHEET 2 OF 4 PIVOTALARM BAND SAW This is a division of application Ser. No. 086,732, filedNov. 4, 1970, now U.S. Pat. No. 3,682,030.

BACKGROUND OF THE INVENTION The present invention relates in general toband saws which employ a continuous loop-type blade and, moreparticularly, relates to band saws having a blade carrying arm which ispivotally secured to a support for raising and lowering of the sameduring the cutting process.

A number of different uses for the continuous loop band saw have evolvedin industry today, and a number of different band saw constructions havesimilarly been developed. It has been a constant goal of manufacturersof sawing equipment to develop saws which will cut with a high degree ofaccuracy. Therefore, problems such as wandering of the saw blade ormisalignment of the blade carrying arm during the cutting process can bequite serious and result in very unsatisfactory performance of the saw.

One approach to the construction of a band saw which will produce arelatively accurate saw out has been to employ a saw arm which is raisedand lowered on four or more posts in a manner similar to an elevator.This construction has enabled band saws to be produced which arerelatively accurate in their cutting capability, but the raising andlowering mechanisms have been found to be expensive to manufacture andsometimes inconvenient to use.

Another approach has been to employ a pivoted arm or hinge-type bandsaw, which is secured to a support at one end of the arm for arcuatemotion during the cutting process. While this approach has resulted in aband saw which is much less expensive to manufacture, the cuttingaccuracy of the pivotal or hinge-type band saw has suffered. One pivotalarm band saw construction which is in widespread use mounts the sawblade carrying arm to the supporting frame in a manner which induces amoment in the pivotal shaft causing the shaft to be slightly angularlydisplaced during cutting. While this slight displacement is tolerable insome operations, for others the arm mounting construction is veryunsatisfactory and results in crooked cutting of the work piece. Inaddition, it has been common practice to locate the hinge or pivotalmounting for the arm to the support at a position substantially belowthe work surface on which the piece is being cut. As will be more fullyexplained hereinafter, said saw configurations result in a variable andundesirable downward force on the cutting blade, which is eitherattempted to be compensated for by further apparatus or results inundesirable cutting rates and blade breakage.

Certain other problems have been frequently encountered with pivotal armband saws. It has been found to be difficult to maintain the continuousloop band saw blade on the drive and idler wheels. One approach to asolution to this problem has been to construct wheels which are formedto prevent the band saw blade from climbing off the wheels. The band sawblade may, however, also come off the wheels if the drive wheel goesinto slip-condition. Thus, when there is a heavy load on the saw blade,it is possible for the drive wheel to begin to slip relative to the bandsaw blade which it is frictionally driving. When this occurs, the bladeon present band saws will very often slide off the wheels. There havealso been numerous problems in twisting of the band saw bladeintermediately of the wheels and guiding the same for proper cutting.Similarly, the distribution of coolant over the band saw blade in thearea of cutting has been very difficult, since an improper distributionof the coolant material will result in inaccurate cutting. Some guideconstruc tions induce localized stress forces in the continuous loop sawblade which result in fatigue and breaking of the saw blade. Finally, avariety of control systems have been employed in seeking to control therate of descent of the pivotal arm saw blade. Many of these systems areeither very complex in nature or are not easily and convenientlyadjustable to the different rate of arm descent.

Accordingly, it is an object of the present invention to provide apivotal arm band saw construction which results in improved accuracy anduniformity of cut of the saw blade.

It is another object of the present invention to provide a pivotal armband saw construction in which the rate of cutting of the saw can beaccurately controlled and readily varied.

It is another object of the present invention to provide a pivotal armband saw in which the continuous loop saw blade is retained on the driveand idler wheels through a greater variety of operating conditions.

It is still a further object of the present invention to provide apivotal arm band saw in which the saw blade is cooled by a liquidcoolant and guided for uniform cutting while minimizing the fatigueexperienced by the blade during cutting.

It is another object of the present invention to provide a pivotal armband saw which is relatively easy to manufacture and enables accurateand reproducible saw cuts, is easy to maintain and repair, and may beeasily adjusted to a variety of operating conditions.

The pivotal arm band saw of the present invention has further objectsand features of advantage which will be more fully set forthhereinafter.

SUMMARY OF THE INVENTION The pivotal arm band saw of the presentinvention is comprised briefly of a support, an arm having a saw bladecarrying portion, and pivotal connection means extending transversely ofthe arm and pivotally securing the arm to the support for guided arcuatemotion in a single plane, a pair of wheels formed for receipt andcarrying of a continuous loop band saw blade, each of the wheels beingrotatably mounted to the carrying portion of the arm in relativelyspaced positions thereon, the connection means being formed to pivotallysecure the arm to the support at laterally spaced positions on thesupport disposed on both sides of the plane of travel of the saw bladethrough the work piece. The pivotal connection is further preferablyabove the work supporting surface on which material is cut.

In another aspect of the present invention, a frustoconical drivingwheel is employed having a saw blade retaining means position adjacentthe small diameter end of the frustoconical peripheral surface of thedriving wheel to engage the smooth back edge of the saw blade. The bladeretaining means is preferably comprised of a flange fixed to the smalldiameter side of the wheel.

In still another aspect of the present invention, saw blade guide meansare provided which are formed for the replacement of saw blade engagingguide elements and to direct a liquid coolant down upon the back edge ofthe saw blade. The guide elements further preferably impart a positivecamber to the saw blade to reduce fa tiguing.

In still another aspect of the present invention, fluid activatedcontrol means including a gas-liquid system for raising and controllingthe rate of descent of the pivotal arm is provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side perspective view of apivotal arm band saw constructed in accordance with the presentinvention.

FIG. 2 is a side elevational view of the band saw of FIG. 1.

FIG. 3 is a top plan view of the band saw of FIG. 1.

FIG. 4 is a fragmentary top view of the pivotal arm as illustrated inFIG. 3.

FIG. 5 is a side elevational view of the pivotal arm illustrated in FIG.4.

FIG. 6 is an enlarged, fragramentary top view of the pivotal armillustrating a drive wheel construction in accordance with the presentinvention.

FIG. 7 is a further enlarged, fragramentary view of an idler wheelconstructed in accordance with the present invention.

FIG. 8 is a further enlarged, fragramentary view of a drive wheelconstructed in accordance with the present invention.

FIG. 9 is an enlarged, fragramentary view of a drive wheel constructedin accordance with the present invention with a band saw bladepositioned thereon.

FIG. 10 is another enlarged, fragramentary view of a drive wheelconstructed in accordance with the present invention with a band sawblade positioned thereon.

FIG. 11 is an enlarged, fragramentary side elevational view of a guidemember constructed in accordance with the present invention.

FIG. 12 is an enlarged, fragramentary end elevational view of the guidemeans of FIG. 11.

FIG. 13 is a schematic representation ofa fluid actuated controlmechanism constructed in accordance with the present invention andemployed to raise and lower the band saw arm.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1, 2, and 3,the basic elements of the pivotal arm band saw of the present inventioncan be examined. The band saw includes a support, generally designated11, to which an arm, generally designated 12, is pivotally secured bypivotal mounting means 13. Rotatably mounted to arm 12 are a pair ofwheels 16 and 17, with wheel 16 being connected to motor 18 throughpower drive speed reducer 19. As illustrated in the drawings, frame 11includes feed table 21 having work supporting rollers 22 and 23 and workadvancing vices 24 and 26, preferably formed as described in mypreviously issued U.S. Pat. No. 3,504,585. Support frame 11 furtherincludes upstanding legs 27, 28 and 29 as well as a chip and coolantreceiving tray 31. Vice 26 is mounted on top of bench 32 over thecoolant and chip tray and provides a work supporting surface 33, bestseen in FIG. 2.

In order to insure and improve the cutting characteristics of thepivotal arm band saw, the saw of the present invention is constructedwith a pivotal mounting to the frame which minimizes possible. angulardisplacements of the arm relative to the frame during cutting. Themounting structure of the present invention may best be seen byreference to FIGS. 3, 4, and 5. Pivotal connection means 13 may be seento be comprised of a pair of bearing housings 36 and 37 and transverselyextending shaft 38 mounted between the bearing housings for rotationtherein. As may be seen in FIG. 1, the bearing housings 36 and 37 aresecured to frame 11 for support of the pivotal arm. Extending from andsecured to shaft 38 is a portion 39 of arm 12, which is preferablywelded by welds 41 to shaft 38. Portion 39 is further connected to aC-shaped arm body 42 upon which wheels 16 and 17 are rotatably mounted.

Thus, as best may be seen in FIG. 5, arm 12 includes portion 39 andC-shape portion 42 which are fixedly secured to shaft 38 for pivotalmotion as mounted to frame 11.

It is a feature of the pivotal arm band saw of the present inventionthat the bearing housings 36 and 37 are positioned in a manner toimprove the accuracy of the saw cuts which can be achieved with thepresent pivotal band saw. As best may be seen in FIG. 4, drive wheels 16and 17 are in general alignment and have continuous loop saw blade 43mounted thereon and extended therebetween. The wheels 16 and 17 and sawblade 43, as twisted by the guides for cutting, are all disposedsubstantially along plane 44, the plane of rotation of the wheels andtravel of blade 43 through the work piece. Bearing housings 36 and 37may be seen to be disposed on either side of plane 44 to thus secure thepivotal arm 12 to frame 11 from positions laterally spaced on both sidesof the plane travel of said saw blade and, in this case, the plane ofrotation of the wheels. The effect of so positioning bearing housings 36and 37 is very important. As the saw blade passes through the workpiece, the cutting force is transferred from the saw blade to the wheelsand from there to portion 39 of the arm. The force induced in portion 39of the arm is resisted by bearing forces in housings 36 and 37. When thehousings 36 and 37 are positioned on both sides of plane 44, the bearinghousings 36 and 37 both exert forces L in the direction indicated inFIG. 4 against shaft 38. This loading force L is induced when the bladetravels as indicated by the arrow in FIGS. 4 and 5. If the bearinghousing 37 were disposed on the same side of plane 44 as is housing 36,an entirely different set of reaction forces would be induced in thebearing housings. More particularly, the load force L on bearing housing37 when positioned on the other side of plane 44 would be in theopposite direction as illustrated in FIG. 4. This type of pivotalmounting is common in present pivotal arm band saws. When the loadingforce in housing 37 is in the opposite direction than that shown in FIG.4, there exists a coupling of the loading forces which results inangular displacements of shaft 38. Thus, shaft 38 tends to twist in thebearing housings and arm 12 correspondingly is subject to angulardeflection about a vertical axis. Since it is impossible to completelyeliminate all play from between the bearing housings and shaft 38, suchangular deflection, when multiplied by the length of arm 12, can resultin substantial inaccuracy in cutting at the point at which the saw bladeengages the work. In the present invention the pivotal connection meansis formed so that any play between housings 36 and 37 and the shaft 38does not result in an angular displacement of arm 12. Instead anydisplacement is generally aligned with the place of cutting of theblade, which does not result in an inaccurate saw cut.

Since it is possible to mount wheels 16 and 17 at an angle to plane 44while still twisting blade 43 to out along plane 44, the plane ofrotation of the wheels and the plane of travel of the saw blade throughthe work piece may not coincide. Since the arm is loaded by the force onthe blade, the bearing housings should be on both sides of the blade. Itshould be further noted that plane 44 need not be verticle.

It is a further feature of the pivotal arm band saw of the presentinvention that the connection means to support 11 is positioned in amanner which tends to minimize the differences in cutting rate and forceon the cutting blade which result by reason of the inherent arcuatemotion of saws of this type. As may best be seen in FIG 5, pivotal shaft38 is mounted in housings 36 and 37 at a distance D above generallyhorizontally extending work supporting surface 33. Additionally, thedistance D is preferably selected to be equal to about one half thethickness of the material to be cut. This distance can be approximatedfor a given size band saw and an average thickness work piece. In priorband saw constructions the pivotal arm has most frequently affixed at orbelow the work supporting surface. The positioning of the pivotalmounting means at or below the work supporting surface results in thedownward gravitational forces on the pivotal arm, and thus the sawblade, increasing substantially as the saw blade is lowered from a fullraised position to a full lowered position during cutting. Thus, whenthe saw blade is in raised position, the downward gravitational forcesare at a minimum while when it is in the lowered position the forces areat a maximum. The change in the downward force is a function of thecosine of the angle of the pivotal arm to the horizon. When the pivotalarm is pivoted from a position below the work supporting surface, thecosine of the angle varies substantially from the full raised to thefull lowered position. Conversely, however, the positioning of thepivotal arm as illustrated in the present invention results in arelatively uniform downward gravitational force being applied to the sawblade. This is particularly true where the connection means secures thearm to the support at a distance above the support surface equal toabout one half of the material to be cut. The change in cosine andtherefore the change in downward gravitational force is minimized whenthe pivotal connection means is positioned at a distance equal to aboutone half the thickness of the material to be cut.

The distance D above the support surface can be preset to approximatethe optimum distance for expected use of the band saw. Pivotal arm orhinged band saws normally employ a continuous loop band saw blade havinga height from the cutting teeth to the smooth back edge in the range ofabout 1/2 inch to about 1% inches. Occasionally, even band saw bladeswhich are 2 inches in height may be used. The height of the band icutting will be achieved if the work piece has a diameter of about threeinches. Accordingly, the distance D above the work surface for a l/2inch saw blade for minimization of the cosine effect would be [V2 inchesor l/2 of the 3 inch diameter piece being cut. As the saw blade heightis increased by l/4 inch to 3/4 inches the diameter at which maximumcutting efficiency occurs is increased by 2 inches from 3 inches to 5inches. Therefore, the distance D will be increased by l inch tomaintain a minimum cosine effect. It has been found that for saw bladeheight above l/2 inch, at which the distance D is optimally 1%. inches,each increment of saw blade height of H2 inch increases the distance Dby about I inch in order that the saw may be set up to cut at maximumefficiency with a minimization of the effect of the change in thelocation of the center of gravity of the saw arm relative to the pivotduring cutting. Minimization of the cosine effect further allows theguides to be set closer together, which in turn insures more accuratecutting and less blade fatigue.

In order to further minimize the effect of the change in the location ofthe center of gravity of pivotal arm 12 during arcuate motion, it is afurther feature of the band saw of the present invention that mountingmeans 13 be positioned at a substantial distance from the area in whichthe cutting occurs. As will be seen in FIGS. 3, 4, and 5, pivotal shaft38 is positioned so that it passes transversely of drive wheel 16 with aportion 46 of shaft 38 maintained in substantial clearance from theperipheral edge of drive wheel 16. Such clearance allows saw blade 43 tobe conveniently mounted on the drive and idler wheels by slipping theblade on the wheels as is commonly done in existing band saws. Suchclearance is also necessary in order to have the bearing housing 37positioned on the side of plane 44 as above described. Additionally,however, the positioning of shaft 38 beyond a plane (not shown) passingperpendicular to support surface 33 tangential to the periphery of wheel16 has the effect of increasing the distance between pivotal shaft 38and vice 26 over pivotal arm saws previously employed. This increase indistance has a twofold beneficial effect. First, a greater distanceresults in greater vertical displacement at vice 26 for a given angle ofpivot of arm 12. Therefore, one need only raise the arm 12 to arelatively small arcuate angle to accommodate a large work piece. Thesmall angular displacement results again in assisting the minimizationof the change in location of the center of gravity of the arm whichcooperates with the positioning of the arm above work surface 33, aspreviously explained. Secondly, and very importantly, increasing thedistance between the pivotal shaft and the work holding vice has theeffect of allowing the saw blade guide members 51 and 52, best seen inFIG. 2, to be set more closely together to conform to the thickness ofthe work piece. Saw blade members 51 and 52 are secured to arm 12 forarcua'te motion therewith. Accordingly, when the arm must pass through asubstantial arc in order to cut the work piece, the movable guide member52 must be positioned at a greater distance from fixed guide member 51than is necessary for smaller angular displacements. As the distancebetween the guide members increases, the saw blade is subjected togreater bending forces and may uncontrollably and unpredictably bedisplaced during cutting. Therefore, increasing the distance from thepivot to the cutting area decreases the angle through which the arm mustbe articulated during cutting and allows the guides to be set moreclosely together for better support of the saw blade throughout the cut.

In a further effort to improve the overall performance of pivotal-typeband saws, it is a feature of another aspect of the present invention toprovide a band saw drive wheel which affords a more reliable and troublefree operation of the band saw. The drive wheel construction of thepresent invention can best be understood by reference to FIGS. 6 and 8in which drive wheel 16 can be seen to be rotatably mounted to arm 12 byshaft 61. The drive wheel is formed with a generally circular wheel bodywhich terminates in a peripheral saw blade engaging surface 62. Surface62 is formed as a frusto-conical surface about the central axis 63 ofthe wheel. As best may be seen in FIG. 8, the wheel tapers from largediameter side 64 to a small diameter side 66, with the angle of taperdesignated as alpha Peripheral surface 62 has a height along axis 63sufficient to frictionally engage a substantial portion of one of theflat blade sides in order to dry the blade. As shown in FIGS. 6-and 7the small diameter end 66 of the drive wheel is provided with a sawblade retaining means in the form of a side flange element 67 secured toand extending from the drive wheel radially beyond surface 62.

It is well known in the band saw art that the band saw blade will tendto climb up toward the large diameter end of a frusto-conical drivewheel. Accordingly, previous drive wheels have included a flange on thelarge diameter end of the drive wheel to limit the upward climbingaction of the saw blade. While this approach is effective, wheelsconstructed in this manner have been found to have another defect. Whenthe load on the saw blade becomes high, the blade may begin to sliprelative to the drive wheel and in this slip condition the blade tendsto move rapidly toward the small diameter end of the wheel. Thismovement in the slip condition on previous drive wheels has oftenresulted in the band saw jumping off the drive wheel. The drive wheel ofthe present invention is constructed to take advantage of the naturalclimbing tendancy of the saw-blade on the frusto-conical surface andmoreover to guard against jumping of the blade from the drive wheel if aslip condition occurs. Thus, a saw blade retaining means, such as flange67, is positioned adjacent the small diameter end of the drive wheel.During normal operation, the saw blade will climb toward the largediameter end 64 of the drive wheel until it reaches a stable positionthereon, as determined by the position of the fixed guide whichdetermines where the blade enters the wheel. If the loading becomes highenough so that the blade overcomes the frictional forces along surface62, the blade will go into slip condition and drop towards the smalldiameter end of the wheel only to be retained on the wheel by flange 67.

An alternate construction of the blade retaining means suitable for usein the present invention may be seen in FIG. 5. While flange 67 is shownin FIG. 5, it is also possible to eliminate flange 67 and substitutetherefore guide blocks 71, 72, and 73. These guide blocks would bemounted to arm 12 for arcuate motion therewith so as to be constantlypositioned adjacent the small diameter end 66 of the driving wheel. Ifthe retaining means is to be comprised of guide blocks instead of aflange rotating with the wheel, guide block 71 is the most importantblock since it is positioned adjacent the point at which the blade firstengages the drive wheel. This guide block will determine where the bladefirst becomes engaged by the guide to correspondingly determine itsengagement over the periphery of the wheel. Guide blocks 72 and 73 arepreferable since they would assist in retaining the blade on the drivewheel in the event of a slip condition. In addition. a guide block 74may be used adjacent idler wheel 17.

It is a further feature of the present invention to pro vide a drivewheel which will accommodate saw blades of various heights, As best maybe seen in FIGS. 7 through 10, the drive and idler wheels are preferablyformed with a bevelled edge 76 and an axially spaced peripheral groove77, both of which are formed to accommodate the teeth 45 of saw blade43. As may be seen in FIGS. 9 and 10 the teeth 45 of the saw blade aretypically formed in a manner so that they extend inwardly and wouldengage the peripheral surface 62 of the wheel, causing wear of the wheeland damage to the teeth, if it were not for bevelled edge 76 and groove77. Additionally, it is preferable that the drive and idler wheels beformed with a second groove and that flange 67 be tapered as shown.

It is an important feature of the present invention to provide a drivewheel construction which minimizes the strain on the saw blade tothereby reduce the incident of saw blade breakage. It has been foundthat combining the frusto-conical saw blade construction as here andabove described with the skewing of the axis 63 of shaft 61 results inimproved stability of the saw blade on the drive wheel and reduces thestrain and wear on the blade. Axis 63 of shaft 61 is illustrated in FIG.6 as being skewed from a normal position 79 by the angle beta (B).Skewing the axis 63 to the angle beta (B) results in the plane ofrotation of wheel 16 being skewed or rotated about a vertical axis tothe plane of travel of saw blade 43. Thus, the flange 67 at the smalldiameter end of the drive heel may be seen in FIG. 6 to be displacedaway from saw blade 43. Displacement of flange 67 away from saw blade 43at the points of engagement and disengagement of the saw blade has thebeneficial effect of avoiding rubbing the edge of the saw blade withflange 37. In prior wheel constructions such rubbing has been found tofatigue the saw blade and to some extent the drive wheel. It should benoted further that skewing the plane of rotation of the drive wheelthrough angle beta (,8) has the effect, when combined with the anglealpha (a) of frustoconical surface 62, of orienting side 81 of the drivewheel almost perpendicular to the plane of travel of the saw blade. Thisis important since without the skewed plane of rotation, angle alpha (a)will tend to cause the saw blade to be slightly elongated adjacent theteeth which would in turn induce greater stress in the side of the bladeadjacent the teeth and the smooth back edge.

It is a further feature of the present invention to provide an idlerwheel whichis similarly frusto-conical and has a large diameter end 82and a small diameter end 83. The idler wheel, however, is formed with aflange 84 adjacent the large diameter end. Flange 84 is in generalalignment with flange 67,'but wheel 17 is formed in a manner as has beenpreviously attempted for drove wheels. Since wheel 17 is not a drivewheel, this construction is adequate for idler wheels since the slippingcondition occurs only at drive wheel 16. Moreover, the

combination of an idler wheel with a flange at the large diameter endand a drive wheel with a flange at the small diameter end tends toreduce the incidents of slipping and virtually completely eliminatejumping of the saw blade from the drive and idler wheels. It should benoted that the central axis 86 of shaft 87 is approximately normal tothe line of travel of blade 43 for idler wheel 17.

In order to provide further for accurate saw blade cutting, it is afurther feature of another aspect of the present invention to formguides 51 and 52 in a manner enhancing the uniformity of the saw bladecuts. As may be seen in FIG. 2, saw blade guide means is comprised ofguiding elements 51 and 52 which are mounted on bar member 53. Guide 51is fixedly secured to bar member 53 while guide 52 is formed with means54 for allowing selective clamping of guide member 52 at variouspositions along bar 53. Thus, guide member 52 is a movable guide whichcan be laterally adjusted along bar 53 in order to accommodate variouswidth work pieces. As is common practice, guide members 52 and 53 imparta twist, usually about ninety degrees, to saw blade 43 in order that thesaw blade at the area of cutting will be parallel to the arcuate motionof arm 12. Since the guides impart a twist to blade 43 and such twistingcan induce stress concentrations and fatiguing, it is another feature ofthe present invention to position a fixed guide between wheels 16 and 17at a distance from wheel 17 such that when movable guide 52 is separatedfrom fixed guide 51 by distance equal to about four to 12 times theheight of the saw blade, movable guide 52 will be spaced approximatelythe same distance from wheel 17 as fixed guide 51 is from wheel 16.Thus, the degree of twisting of the saw blade from idler wheel 17 tomovable guide 52 and from fixed guide 51 to drive wheel 16 will beapproximately equal. Fatiguing of the saw blade as a result of the twistimparted therein is, therefore, minimized by balancing the amount oftwisting.

A more detailed illustration of the guide members of the presentinvention is shown in FIGS. 11 and 12. In order to effect cooling of thesaw blade it is preferable that the saw blade have a coolant passed overthe same in the area of the work piece to transfer heat and convey chipsor particles which are cut away from the work piece. The guide elementshown in FIGS. 11 and 12 is formed for distribution of coolant over thesaw blade and additionally to provide bearing surfaces which guide theblade to a vertical position between the guide members. The guide memberillustrated is designated as the movable member 52, although the fixedguide member is preferably similarly formed. Guide member 52 iscomprised of a downwardly extending arm 91 which is secured at the upperend to bar 53. Detachably mounted on arm 91 is a second piece or member92, which is held to the member by a bolt 93. The lower ends of pieces91 and 92 have guide elements 94, 95, and 96 removably secured thereto.The guide elements may be carbide guides which are formed for sliding engagement with the smooth sides of the saw blade. As will be seen, guideelements 95 and 96 engage the sides of the saw blade, while guideelement 94 engages'the smooth back edge 47 of the saw blade. Element 94is further preferably eccentrically mounted to member 52 by fastener100. This allows element 94 to be inverted to displace blade 43downwardly when smaller blades are used to be certain to impart apositive camber (discussed in detail below).

In order to provide a coolant flow over blade 43, it is preferable thatthe two pieces of the guide member be formed with a coolant channel 97.As will be seen from the drawings, coolant channel 97 is first formed asa bore in member 91 having a threaded end 98 to receive coolant conduit99. Channel 97 then continues to be formed in both pieces 91 and 92 ofthe guide member and terminates in discharge opening 101. As thusformed, the coolant will have imparted thereto a substantial downwardvelocity as it travels through channel 97 and is discharged over theback smooth edge 47 of the saw blade. It is important to note that thedischarge opening 101 is positioned over the back edge of the saw bladeso that a substantial and equal amount of the discharge opening ispositioned on either side of the blade. This tends to cause the blade torun evenly between the guide elements and 96, as opposed to beingdisplaced preferentially towards one of the guide ele ments. Inaddition, discharge opening 101 is preferably relieved at 102 in orderthat coolant will tend to travel in the direction of travel of saw blade43, as indicated by the arrow.

In a further effort to enhance characteristics of the band saw of thepresent invention and particularly to reduce fatiguing of the saw blade,it is a feature of the present invention that the guide elementsandguide members be formed in position so as to impart a positive camber tothe saw blade. The concept of camber can best by understood by referenceto FIG. 5. If the saw blade is extended between wheels 16 and 17 withouta twist induced therein by the guide members, the saw blade will assumea position approximately on a line tangent to both of the wheels. Upontwisting of the saw blade, however, the back edge 47 will rise above thetangential line and the teeth will drop below, with the middle of thesaw blade laying substantially along the tangential line between thedrive wheel and idler wheel. If the saw blade is supported between theguide member in this position, the cutting force will tend to cause theblade to be upwardly displaced so that the center of the blade is nowabove the tangent between the two wheels. Such displacement is oftenreferred to as a negative camber. As will be appreciated, a negativecamberinduces stress forces on the back side 47 of the saw blade. Inorder to attempt to avoid this phenomenon, the guide element 94 and thelength of arm 91 are selected so that the center of blade 43 isdisplaced below the tangent between the drive and idler wheels tothereby impart a positive camber to the saw blade. It is interesting tonote further that since the guide bar 53 on which movable guide 52 ismounted is horizontal and therefore parallel to a line drawntangentially between the guide and idler wheels, guide member 52 willmaintain a positive camber for all settings along bar 53. Moreover, asthe guide member 52 is moved toward idler wheel 17 the positive camberof the saw blade is increased. This is important since movement towardidler wheel 17 results in a greater span between the guide member and agreater opportunity for upward bending of the saw blade and stressconcentrations in the back edge thereof.

It has been common practice in existing pivotal arm band saws toautomate the raising and lowering of the pivotal arm to some degree.Some saw constructions simply employ a mechanical spring biasingmechanism which tends to counteract changes in the location of thedownward force of gravity on the arm. The spring biasing mechanism isnormally formed to include some manner for limited adjustment in orderto select the rate of drop of the arm. As was set forth hereinabove,however, when the center of gravity of the arm changes substantially dueto substantial changes in the cosine of the angle of the arm, control ofthe rate of descent of the arm becomes very difficult.

It is a further feature of the present invention to provide a fluidactivated controlling means which may be used to control the descent ofthe pivotal arm and thus the cutting characteristics of the saw. As maybe seen in FIG. 2, there is a vertical cylinder 106 which extends fromplatform 32 of the frame and is secured to C- shaped portion 42 of arm12. This cylinder is used to control the rate of descent and to enablelifting of arm 12. The fluid control means employed may best beunderstood by reference to FIG. 13 wherein gas source 107 is connectedby conduit means to valve 108 and liquid reservoir 109. Further conduitmeans connect the liquid reservoir to cylinder 106 in which a piston 111is mounted for reciprocation and is attached to arm 12 as shown in FIGS.2 and 5. In operation valve 108 is a two-way valve which is switched toposition 112 to allow flow of gas from the gas source down conduit 113and conduit 114 to reservoir 109 is pressurized and flows out of conduit117, through conduit 118 and check valve 119 to the piston and cylinder.The flow of liquid 116 between the piston and cylinder causes the pistonto rise which elevates arm 12. As may be seen in FIGS. 2 and 5, theupward motion of arm 12 may be limited by stop means 121 which can beselectively vertically adjusted on the continuous threaded member 122.Once the arm is brought to a fully elevated position, valve 108 may beswitched to position 123 to allow descent of the arm. In the descentmode of the gas-liquid controller, the high pressure gas source 107 isregulated by regulator 124 to have a lower pressure than was required tolift the arm. In addition, regulator 124 is a relieving regulator havinga vent conduit 126 which will vent any pressure in reservoir 109 abovethe regulated preset pressure. If gas source 107 is approximately 1 lp.s.i. and the regulator is set to between about 20 to about 50 p.s.i.,the high pressure in reservoir 109 will be relieved out the relievingregulator and vent 126 upon switching of valve 108 to position 123.Thus, flow of liquid from cylinder 106 will be possible as the weight ofthe arm pushes down on piston 111. The flow will be through conduit 117and liquid metering valve 127, since check valve 119 will now allow aflow from cylinder 106 to reservoir 109. A metered flow rate from thecylinder to the liquid reservoir will result in a controlled descent ofthe arm 12 effected. The rate of control can be determined by varyingthe metering 127 and varying the relieving regulator 124. In the eventthat the pressure over the liquidin the reservoir 109 should drop belowthe regulator pressure, the regulator will allow flow of gas from gassource 107 into the liquid reservoir to control the pressure therein.

It is preferable that the gas source be a standard compressed air sourcewhich would be apart from the band saw illustrated in the drawings,although other gases may be employed. Additionally, liquid 116 ispreferably an oil which is not effected by the moisture normally foundin compressed air and is resistant to oxidation.

I claim:

1. In a band saw including a frame, a pair of relatively spaced apartwheels rotatably mounted to said frame and formed for receipt andcarrying of a continuous loop band saw blade thereon, and guide meansincluding at least one guide member mounted to said frame intermediatesaid wheels and formed to guide and orient a portion of said saw bladefor cutting of a work piece, said guide member being positioned to guidesaid saw blade before said saw blade advances into contact with saidwork piece, said guide member further including a plurality of bladeengaging elements positioned to engage said blade on both sides thereofand formed for sliding engagement with said saw blade, the improvementcomprising:

a coolant channel formed in said guide member and terminating in adischarge opening positioned for discharge of coolant onto the smoothback edge of said saw blade, said discharge opening being positioned andsaid guide member being adapted for flow of said coolant from saiddischarge opening over both sides of said saw blade at a position inadvance of the first engagement of said saw blade with any of said bladeengaging elements in said guide member contacting the sides of said sawblade as said saw blade moves through said guide member.

2. A band saw as defined in claim 1 wherein,

said guide member is formed for flow of coolant against the direction ofmovement of said saw blade during cutting to said position in advance ofthe first engagement of said saw blade with any of said blade guidingelements to enable lubrication of said saw blade after leaving one ofsaid wheels and before engagement by said blade engaging elements.

1. In a band saw including a frame, a pair of relatively spaced apartwheels rotatably mounted to said frame and formed for receipt andcarrying of a continuous loop band saw blade thereon, and guide meansincluding at least one guide member mounted to said frame intermediatesaid wheels and formed to guide and orient a portion of said saw bladefor cutting of a work piece, said guide member being positioned to guidesaid saw blade before said saw blade advances into contact with saidwork piece, said guide member further including a plurality of bladeengaging elements positioned to engage said blade on both sides thereofand formed for sliding engagement with said saw blade, the improvementcomprising: a coolant channel formed in said guide member andterminating in a discharge opening positioned for discharge of coolantonto the smooth back edge of said saw blade, said discharge openingbeing positioned and said guide member being adapted for flow of saidcoolant from said discharge opening over both sides of said saw blade ata position in advance of the first engagement of said saw blade with anyof said blade engaging elements in said guide member contacting thesides of said saw blade as said saw blade moves through said guidemember.
 2. A band saw as defined in claim 1 wherein, said guide memberis formed for flow of coolant against the direction of movement of saidsaw blade during cutting to said position in advance of the firstengagement of said saw blade with any of said blade guiding elements toenable lubrication of said saw blade after leaving one of said wheelsand before engagement by said blade engaging elements.